1 The Purpose of the Rails Router
The Rails router matches incoming HTTP requests to specific controller actions in your Rails application based on the URL path. (It can also forward to a Rack application.) The router also generates path and URL helpers based on the resources configured in the router.
1.1 Routing Incoming URLs to Code
When your Rails application receives an incoming request, it asks the router to match it to a controller action (aka method). For example, take the following incoming request:
GET /users/17
If the first matching route is:
get '/users/:id', to: 'user#show'
The request is matched to the UsersController
class's show
action with { id: '17' }
in the params
hash.
The to:
option expects a controller#action
format when passed a string. Alternatively, You can pass a symbol and use the action:
option, instead of to:
. You can also pass a string without a #
, in which case the controller:
option is used instead to to:
. For example:
get '/users/:id', controller: 'users', action: :show
Rails uses snake_case for controller names when specifying routes. For example, if you have a controller named UserProfilesController
, you would specify a route to the show action as user_profiles#show
.
1.2 Generating Paths and URLs from Code
The Router automatically generates path and URL helper methods for your application. With these methods you can avoid hard-coded path and URL strings.
For example, the user_path
and user_url
helper methods are available when defining the following route:
get '/users/:id', to: 'users#show', as: 'user'
The as:
option is used to provide a custom name for a route, which is used when generating URL and path helpers.
Assuming your application contains this code in the controller:
@user = User.find(params[:id])
and this in the corresponding view:
<%= link_to 'User Record', user_path(@user) %>
The router will generate the path /users/17
from user_path(@user)
. Using the user_path
helper allows you to avoid having to hard-code a path in your views. This is helpful if you eventually move the route to a different URL, as you won't need to update the corresponding views.
It also generates user_url
, which has a similar purpose. While user_path
generates a relative URL like /users/17
, user_url
generates an absolute URL such as https://example.com/users/17
in the above example.
1.3 Configuring the Rails Router
Routes live in config/routes.rb
. Here is an example of what routes look like in a typical Rails application. The sections that follow will explain the different route helpers used in this file:
Rails.application.routes.draw do
resources :brands, only: [:index, :show] do
resources :products, only: [:index, :show]
end
resource :basket, only: [:show, :update, :destroy]
resolve("Basket") { route_for(:basket) }
end
Since this is a regular Ruby source file, you can use all of Ruby's features (like conditionals and loops) to help you define your routes.
The Rails.application.routes.draw do ... end
block that wraps your route definitions is required to establish the scope for the router DSL (Domain Specific Language) and must not be deleted.
Be careful with variable names in routes.rb
as they can clash with the DSL methods of the router.
2 Resource Routing: the Rails Default
Resource routing allows you to quickly declare all of the common routes for a given resource controller. For example, a single call to resources
declares all of the necessary routes for the index
, show
, new
, edit
, create
, update
, and destroy
actions, without you having to declare each route separately.
2.1 Resources on the Web
Browsers request pages from Rails by making a request for a URL using a specific HTTP verb, such as GET
, POST
, PATCH
, PUT
, and DELETE
. Each HTTP verb is a request to perform an operation on the resource. A resource route maps related requests to actions in a single controller.
When your Rails application receives an incoming request for:
DELETE /photos/17
it asks the router to map it to a controller action. If the first matching route is:
resources :photos
Rails would dispatch that request to the destroy
action on the PhotosController
with { id: '17' }
in params
.
2.2 CRUD, Verbs, and Actions
In Rails, resourceful routes provide a mapping from incoming requests (a combination of HTTP verb + URL) to controller actions. By convention, each action generally maps to a specific CRUD operation on your data. A single entry in the routing file, such as:
resources :photos
creates seven different routes in your application, all mapping to the PhotosController
actions:
HTTP Verb | Path | Controller#Action | Used to |
---|---|---|---|
GET | /photos | photos#index | display a list of all photos |
GET | /photos/new | photos#new | return an HTML form for creating a new photo |
POST | /photos | photos#create | create a new photo |
GET | /photos/:id | photos#show | display a specific photo |
GET | /photos/:id/edit | photos#edit | return an HTML form for editing a photo |
PATCH/PUT | /photos/:id | photos#update | update a specific photo |
DELETE | /photos/:id | photos#destroy | delete a specific photo |
Since the router uses the HTTP verb and path to match inbound requests, four URLs can map to seven different controller actions. For example, the same photos/
path matches to photos#index
when the verb is GET
and photos#create
when the verb is POST
.
Order matters in the routes.rb
file. Rails routes are matched in the order they are specified. For example, if you have a resources :photos
above a get 'photos/poll'
the show
action's route for the resources
line will be matched before the get
line. If you want the photos/poll
route to match first, you'll need to move the get
line above the resources
line.
2.3 Path and URL Helpers
Creating a resourceful route will also expose a number of helpers to controllers and views in your application.
For example, adding resources :photos
to the route file will generate these _path
helpers:
Path Helper | Returns URL |
---|---|
photos_path |
/photos |
new_photo_path |
/photos/new |
edit_photo_path(:id) |
/photos/:id/edit` |
photo_path(:id) |
/photos/:id |
Parameters to the path helpers, such as :id
above, are passed to the generated URL, such that edit_photo_path(10)
will return /photos/10/edit
.
Each of these _path
helpers also have a corresponding _url
helper (such as photos_url
) which returns the same path prefixed with the current host, port, and path prefix.
The prefix used before "_path" and "_url" is the route name and can be identified by looking at the "prefix" column of the rails routes
command output. To learn more see Listing Existing Routes below.
2.4 Defining Multiple Resources at the Same Time
If you need to create routes for more than one resource, you can save a bit of typing by defining them all with a single call to resources
:
resources :photos, :books, :videos
The above is a shortcut for:
resources :photos
resources :books
resources :videos
2.5 Singular Resources
Sometimes, you have a resource that users expect to have only one (i.e. it does not make sense to have an index
action to list all values of that resource). In that case, you can use resource
(singular) instead of resources
.
The below resourceful route creates six routes in your application, all mapping to the Geocoders
controller:
resource :geocoder
resolve('Geocoder') { [:geocoder] }
The call to resolve
is necessary for converting instances of the Geocoder
to singular routes through record identification.
Here are all of the routes created for a singular resource:
HTTP Verb | Path | Controller#Action | Used to |
---|---|---|---|
GET | /geocoder/new | geocoders#new | return an HTML form for creating the geocoder |
POST | /geocoder | geocoders#create | create the new geocoder |
GET | /geocoder | geocoders#show | display the one and only geocoder resource |
GET | /geocoder/edit | geocoders#edit | return an HTML form for editing the geocoder |
PATCH/PUT | /geocoder | geocoders#update | update the one and only geocoder resource |
DELETE | /geocoder | geocoders#destroy | delete the geocoder resource |
Singular resources map to plural controllers. For example, the geocoder
resource maps to the GeocodersController
.
A singular resourceful route generates these helpers:
new_geocoder_path
returns/geocoder/new
edit_geocoder_path
returns/geocoder/edit
geocoder_path
returns/geocoder
As with plural resources, the same helpers ending in _url
will also include the host, port, and path prefix.
2.6 Controller Namespaces and Routing
In large applications, you may wish to organize groups of controllers under a namespace. For example, you may have a number of controllers under an Admin::
namespace, which are inside the app/controllers/admin
directory. You can route to such a group by using a namespace
block:
namespace :admin do
resources :articles
end
This will create a number of routes for each of the articles
and comments
controller. For Admin::ArticlesController
, Rails will create:
HTTP Verb | Path | Controller#Action | Named Route Helper |
---|---|---|---|
GET | /admin/articles | admin/articles#index | admin_articles_path |
GET | /admin/articles/new | admin/articles#new | new_admin_article_path |
POST | /admin/articles | admin/articles#create | admin_articles_path |
GET | /admin/articles/:id | admin/articles#show | admin_article_path(:id) |
GET | /admin/articles/:id/edit | admin/articles#edit | edit_admin_article_path(:id) |
PATCH/PUT | /admin/articles/:id | admin/articles#update | admin_article_path(:id) |
DELETE | /admin/articles/:id | admin/articles#destroy | admin_article_path(:id) |
Note that in the above example all of the paths have a /admin
prefix per the default convention for namespace
.
2.6.1 Using Module
If you want to route /articles
(without the prefix /admin
) to Admin::ArticlesController
, you can specify the module with a scope
block:
scope module: 'admin' do
resources :articles
end
Another way to write the above:
resources :articles, module: 'admin'
2.6.2 Using Scope
Alternatively, you can also route /admin/articles
to ArticlesController
(without the Admin::
module prefix). You can specify the path with a scope
block:
scope '/admin' do
resources :articles
end
Another way to write the above:
resources :articles, path: '/admin/articles'
For these alternatives (without /admin
in path and without Admin::
in module prefix), the named route helpers remain the same as if you did not use scope
.
In the last case, the following paths map to ArticlesController
:
HTTP Verb | Path | Controller#Action | Named Route Helper |
---|---|---|---|
GET | /admin/articles | articles#index | articles_path |
GET | /admin/articles/new | articles#new | new_article_path |
POST | /admin/articles | articles#create | articles_path |
GET | /admin/articles/:id | articles#show | article_path(:id) |
GET | /admin/articles/:id/edit | articles#edit | edit_article_path(:id) |
PATCH/PUT | /admin/articles/:id | articles#update | article_path(:id) |
DELETE | /admin/articles/:id | articles#destroy | article_path(:id) |
If you need to use a different controller namespace inside a namespace
block you can specify an absolute controller path, e.g: get '/foo', to: '/foo#index'
.
2.7 Nested Resources
It's common to have resources that are logically children of other resources. For example, suppose your application includes these models:
class Magazine < ApplicationRecord
has_many :ads
end
class Ad < ApplicationRecord
belongs_to :magazine
end
Nested route declarations allow you to capture this relationship in your routing:
resources :magazines do
resources :ads
end
In addition to the routes for magazines, this declaration will also route ads to an AdsController
. Here are all of the routes for the nested ads
resource:
HTTP Verb | Path | Controller#Action | Used to |
---|---|---|---|
GET | /magazines/:magazine_id/ads | ads#index | display a list of all ads for a specific magazine |
GET | /magazines/:magazine_id/ads/new | ads#new | return an HTML form for creating a new ad belonging to a specific magazine |
POST | /magazines/:magazine_id/ads | ads#create | create a new ad belonging to a specific magazine |
GET | /magazines/:magazine_id/ads/:id | ads#show | display a specific ad belonging to a specific magazine |
GET | /magazines/:magazine_id/ads/:id/edit | ads#edit | return an HTML form for editing an ad belonging to a specific magazine |
PATCH/PUT | /magazines/:magazine_id/ads/:id | ads#update | update a specific ad belonging to a specific magazine |
DELETE | /magazines/:magazine_id/ads/:id | ads#destroy | delete a specific ad belonging to a specific magazine |
This will also create the usual path and url routing helpers such as magazine_ads_url
and edit_magazine_ad_path
. Since the ads
resource is nested below magazines
, The ad URLs require a magazine. The helpers can take an instance of Magazine
as the first parameter (edit_magazine_ad_path(@magazine, @ad)
).
2.7.1 Limits to Nesting
You can nest resources within other nested resources if you like. For example:
resources :publishers do
resources :magazines do
resources :photos
end
end
In the above example, the application would recognize paths such as:
/publishers/1/magazines/2/photos/3
The corresponding route helper would be publisher_magazine_photo_url
, requiring you to specify objects at all three levels. As you can see, deeply nested resources can become overly complex and cumbersome to maintain.
The general rule of thumb is to only nest resources 1 level deep.
2.7.2 Shallow Nesting
One way to avoid deep nesting (as recommended above) is to generate the collection actions scoped under the parent - so as to get a sense of the hierarchy, but to not nest the member actions. In other words, to only build routes with the minimal amount of information to uniquely identify the resource.
The "member" actions are the ones that apply to an individual resource and require an ID to identify the specific resource they are acting upon, such as show
, edit
, etc. The "collection" actions are the ones that act on the entire set of the resource, such as index
.
For example:
resources :articles do
resources :comments, only: [:index, :new, :create]
end
resources :comments, only: [:show, :edit, :update, :destroy]
Above we use the :only
option which tells Rails to create only the specified routes. This idea strikes a balance between descriptive routes and deep nesting. There is a shorthand syntax to achieve just that, via the :shallow
option:
resources :articles do
resources :comments, shallow: true
end
This will generate the exact same routes as the first example. You can also specify the :shallow
option in the parent resource, in which case all of the nested resources will be shallow:
resources :articles, shallow: true do
resources :comments
resources :quotes
end
The articles resource above will generate the following routes:
HTTP Verb | Path | Controller#Action | Named Route Helper |
---|---|---|---|
GET | /articles/:article_id/comments(.:format) | comments#index | article_comments_path |
POST | /articles/:article_id/comments(.:format) | comments#create | article_comments_path |
GET | /articles/:article_id/comments/new(.:format) | comments#new | new_article_comment_path |
GET | /comments/:id/edit(.:format) | comments#edit | edit_comment_path |
GET | /comments/:id(.:format) | comments#show | comment_path |
PATCH/PUT | /comments/:id(.:format) | comments#update | comment_path |
DELETE | /comments/:id(.:format) | comments#destroy | comment_path |
GET | /articles/:article_id/quotes(.:format) | quotes#index | article_quotes_path |
POST | /articles/:article_id/quotes(.:format) | quotes#create | article_quotes_path |
GET | /articles/:article_id/quotes/new(.:format) | quotes#new | new_article_quote_path |
GET | /quotes/:id/edit(.:format) | quotes#edit | edit_quote_path |
GET | /quotes/:id(.:format) | quotes#show | quote_path |
PATCH/PUT | /quotes/:id(.:format) | quotes#update | quote_path |
DELETE | /quotes/:id(.:format) | quotes#destroy | quote_path |
GET | /articles(.:format) | articles#index | articles_path |
POST | /articles(.:format) | articles#create | articles_path |
GET | /articles/new(.:format) | articles#new | new_article_path |
GET | /articles/:id/edit(.:format) | articles#edit | edit_article_path |
GET | /articles/:id(.:format) | articles#show | article_path |
PATCH/PUT | /articles/:id(.:format) | articles#update | article_path |
DELETE | /articles/:id(.:format) | articles#destroy | article_path |
The shallow
method with a block creates a scope inside of which every nesting is shallow. This generates the same routes as the previous example:
shallow do
resources :articles do
resources :comments
resources :quotes
end
end
There are two options that can be used with scope
to customize shallow routes - :shallow_path
and :shallow_prefix
.
The shallow_path
option prefixes member paths with the given parameter:
scope shallow_path: "sekret" do
resources :articles do
resources :comments, shallow: true
end
end
The comments resource here will have the following routes generated for it:
HTTP Verb | Path | Controller#Action | Named Route Helper |
---|---|---|---|
GET | /articles/:article_id/comments(.:format) | comments#index | article_comments_path |
POST | /articles/:article_id/comments(.:format) | comments#create | article_comments_path |
GET | /articles/:article_id/comments/new(.:format) | comments#new | new_article_comment_path |
GET | /sekret/comments/:id/edit(.:format) | comments#edit | edit_comment_path |
GET | /sekret/comments/:id(.:format) | comments#show | comment_path |
PATCH/PUT | /sekret/comments/:id(.:format) | comments#update | comment_path |
DELETE | /sekret/comments/:id(.:format) | comments#destroy | comment_path |
The :shallow_prefix
option adds the specified parameter to the _path
and _url
route helpers:
scope shallow_prefix: "sekret" do
resources :articles do
resources :comments, shallow: true
end
end
The comments resource here will have the following routes generated for it:
HTTP Verb | Path | Controller#Action | Named Route Helper |
---|---|---|---|
GET | /articles/:article_id/comments(.:format) | comments#index | article_comments_path |
POST | /articles/:article_id/comments(.:format) | comments#create | article_comments_path |
GET | /articles/:article_id/comments/new(.:format) | comments#new | new_article_comment_path |
GET | /comments/:id/edit(.:format) | comments#edit | edit_sekret_comment_path |
GET | /comments/:id(.:format) | comments#show | sekret_comment_path |
PATCH/PUT | /comments/:id(.:format) | comments#update | sekret_comment_path |
DELETE | /comments/:id(.:format) | comments#destroy | sekret_comment_path |
2.8 Routing Concerns
Routing concerns allow you to declare common routes that can be reused inside other resources. To define a concern, use a concern
block:
concern :commentable do
resources :comments
end
concern :image_attachable do
resources :images, only: :index
end
These concerns can be used in resources to avoid code duplication and share behavior across routes:
resources :messages, concerns: :commentable
resources :articles, concerns: [:commentable, :image_attachable]
The above is equivalent to:
resources :messages do
resources :comments
end
resources :articles do
resources :comments
resources :images, only: :index
end
You can also call concerns
in a scope
or namespace
block to get the same result as above. For example:
namespace :messages do
concerns :commentable
end
namespace :articles do
concerns :commentable
concerns :image_attachable
end
2.9 Creating Paths and URLs from Objects
In addition to using the routing helpers, Rails can also create paths and URLs from an array of parameters. For example, suppose you have this set of routes:
resources :magazines do
resources :ads
end
When using magazine_ad_path
, you can pass in instances of Magazine
and Ad
instead of the numeric IDs:
<%= link_to 'Ad details', magazine_ad_path(@magazine, @ad) %>
The generated path will be something like /magazines/5/ads/42
.
You can also use url_for
with an array of objects to get the above path, like this:
<%= link_to 'Ad details', url_for([@magazine, @ad]) %>
In this case, Rails will see that @magazine
is a Magazine
and @ad
is an Ad
and will therefore use the magazine_ad_path
helper. An even shorter way to write that link_to
is to specify just the object instead of the full url_for
call:
<%= link_to 'Ad details', [@magazine, @ad] %>
If you wanted to link to just a magazine:
<%= link_to 'Magazine details', @magazine %>
For other actions, you need to insert the action name as the first element of the array, for edit_magazine_ad_path
:
<%= link_to 'Edit Ad', [:edit, @magazine, @ad] %>
This allows you to treat instances of your models as URLs, and is a key advantage to using the resourceful style.
In order to automatically derive paths and URLs from objects such as [@magazine, @ad]
, Rails uses methods from ActiveModel::Naming
and ActiveModel::Conversion
modules. Specifically, the @magazine.model_name.route_key
returns magazines
and @magazine.to_param
returns a string representation of the model's id
. So the generated path may be something like /magazines/1/ads/42
for the objects [@magazine, @ad]
.
2.10 Adding More RESTful Routes
You are not limited to the seven routes that RESTful routing creates by default. You can add additional routes that apply to the collection or individual members of the collection.
The below sections describe adding member routes and collection routes. The term member
refers to routes acting on a single element, such as show
, update
, or destroy
. The term collection
refers to routes acting on multiple, or a collection of, elements, such as the index
route.
2.10.1 Adding Member Routes
You can add a member
block into the resource block like this:
resources :photos do
member do
get 'preview'
end
end
An incoming GET request to /photos/1/preview
will route to the preview
action of PhotosController
. The resource id value will be available in params[:id]
. It will also create the preview_photo_url
and preview_photo_path
helpers.
Within the member
block, each route definition specifies the HTTP verb (get
in the above example with get 'preview'
). In addition to get
, you can
use patch
, put
, post
, or delete
.
If you don't have multiple member
routes, you can also
pass :on
to a route, eliminating the block:
resources :photos do
get 'preview', on: :member
end
You can also leave out the :on
option, this will create the same member route except that the resource id value will be available in params[:photo_id]
instead of params[:id]
. Route helpers will also be renamed from preview_photo_url
and preview_photo_path
to photo_preview_url
and photo_preview_path
.
2.10.2 Adding Collection Routes
To add a route to the collection, use a collection
block:
resources :photos do
collection do
get 'search'
end
end
This will enable Rails to recognize paths such as /photos/search
with GET, and route to the search
action of PhotosController
. It will also create the search_photos_url
and search_photos_path
route helpers.
Just as with member routes, you can pass :on
to a route:
resources :photos do
get 'search', on: :collection
end
If you're defining additional resource routes with a symbol as the first positional argument, be mindful that it is not equivalent to using a string. Symbols infer controller actions while strings infer paths.
2.10.3 Adding Routes for Additional New Actions
To add an alternate new action using the :on
shortcut:
resources :comments do
get 'preview', on: :new
end
This will enable Rails to recognize paths such as /comments/new/preview
with GET, and route to the preview
action of CommentsController
. It will also create the preview_new_comment_url
and preview_new_comment_path
route helpers.
If you find yourself adding many extra actions to a resourceful route, it's time to stop and ask yourself whether you're disguising the presence of another resource.
It is possible to customize the default routes and helpers generated by resources
, see customizing resourceful routes section for more.
3 Non-Resourceful Routes
In addition to resourceful routing with resources
, Rails has powerful support for routing arbitrary URLs to actions. You don't get groups of routes automatically generated by resourceful routing. Instead, you set up each route separately within your application.
While you should usually use resourceful routing, there are places where non-resourceful routing is more appropriate. There's no need to try to force every last piece of your application into a resourceful framework if that's not a good fit.
One example use case for non-resourceful routing is mapping existing legacy URLs to new Rails actions.
3.1 Bound Parameters
When you set up a regular route, you supply a series of symbols that Rails maps to parts of an incoming HTTP request. For example, consider this route:
get 'photos(/:id)', to: 'photos#display'
If an incoming GET
request of /photos/1
is processed by this route, then the result will be to invoke the display
action of the PhotosController
, and to make the final parameter "1"
available as params[:id]
. This route will also route the incoming request of /photos
to PhotosController#display
, since :id
is an optional parameter, denoted by parentheses in the above example.
3.2 Dynamic Segments
You can set up as many dynamic segments within a regular route as you like. Any segment will be available to the action as part of params
. If you set up this route:
get 'photos/:id/:user_id', to: 'photos#show'
This route will respond to paths such as /photos/1/2
. The params
hash will be { controller: 'photos', action: 'show', id: '1', user_id: '2' }.
By default, dynamic segments don't accept dots - this is because the dot is used as a separator for formatted routes. If you need to use a dot within a dynamic segment, add a constraint that overrides this – for example, id: /[^\/]+/
allows anything except a slash.
3.3 Static Segments
You can specify static segments when creating a route by not prepending a colon to a segment:
get 'photos/:id/with_user/:user_id', to: 'photos#show'
This route would respond to paths such as /photos/1/with_user/2
. In this case, params
would be { controller: 'photos', action: 'show', id: '1', user_id: '2' }
.
3.4 The Query String
The params
will also include any parameters from the query string. For example, with this route:
get 'photos/:id', to: 'photos#show'
An incoming GET
request for /photos/1?user_id=2
will be dispatched to the show
action of the PhotosController
class as usual and the params
hash will be { controller: 'photos', action: 'show', id: '1', user_id: '2' }
.
3.5 Defining Default Parameters
You can define defaults in a route by supplying a hash for the :defaults
option. This even applies to parameters that you do not specify as dynamic segments. For example:
get 'photos/:id', to: 'photos#show', defaults: { format: 'jpg' }
Rails would match photos/12
to the show
action of PhotosController
, and set params[:format]
to "jpg"
.
You can also use a defaults
block to define the defaults for multiple items:
defaults format: :json do
resources :photos
resources :articles
end
You cannot override defaults via query parameters - this is for security reasons. The only defaults that can be overridden are dynamic segments via substitution in the URL path.
3.6 Naming Routes
You can specify a name that will used by the _path
and _url
helpers for any route using the :as
option:
get 'exit', to: 'sessions#destroy', as: :logout
This will create logout_path
and logout_url
as the route helpers in your application. Calling logout_path
will return /exit
.
You can also use as
to override routing helper names defined by resources
by placing a custom route definition before the resource is defined, like this:
get ':username', to: 'users#show', as: :user
resources :users
This will define a user_path
helper that will match /:username
(e.g. /jane
). Inside the show
action of UsersController
, params[:username]
will contain the username for the user.
3.7 HTTP Verb Constraints
In general, you should use the get
, post
, put
, patch
, and delete
methods to constrain a route to a particular verb. There is a match
method that you could use with the :via
option to match multiple verbs at once:
match 'photos', to: 'photos#show', via: [:get, :post]
The above route matches GET and POST requests to the show
action of the PhotosController
.
You can match all verbs to a particular route using via: :all
:
match 'photos', to: 'photos#show', via: :all
Routing both GET
and POST
requests to a single action has security
implications. For example, the GET
action won't check for CSRF token (so
writing to the database from GET
request is not a good idea. For more
information see the security guide). In
general, avoid routing all verbs to a single action unless you have a good
reason.
3.8 Segment Constraints
You can use the :constraints
option to enforce a format for a dynamic segment:
get 'photos/:id', to: 'photos#show', constraints: { id: /[A-Z]\d{5}/ }
The above route definition requires id
to be 5 alphanumeric characters long. Therefore, this route would match paths such as /photos/A12345
, but not /photos/893
. You can more succinctly express the same route this way:
get 'photos/:id', to: 'photos#show', id: /[A-Z]\d{5}/
The :constraints
option takes regular expressions (as well as any object that responds to matches?
method) with the restriction that regexp anchors can't be used. For example, the following route will not work:
get '/:id', to: 'articles#show', constraints: { id: /^\d/ }
However, note that you don't need to use anchors because all routes are anchored at the start and the end.
For example:
get '/:id', to: 'articles#show', constraints: { id: /\d.+/ }
get '/:username', to: 'users#show'
The above routes would allow sharing the root namespace and:
- route paths that always begin with a number, like
/1-hello-world
, toarticles
withid
value. - route paths that never begin with a number, like
/david
, tousers
withusername
value.
3.9 Request-Based Constraints
You can also constrain a route based on any method on the Request object that returns a String
.
You specify a request-based constraint the same way that you specify a segment constraint. For example:
get 'photos', to: 'photos#index', constraints: { subdomain: 'admin' }
Will match an incoming request with a path to admin
subdomain.
You can also specify constraints by using a constraints
block:
namespace :admin do
constraints subdomain: 'admin' do
resources :photos
end
end
Will match something like https://admin.example.com/photos
.
Request constraints work by calling a method on the Request object with the same name as the hash key and then comparing the return value with the hash value. For example: constraints: { subdomain: 'api' }
will match an api
subdomain as expected. However, using a symbol constraints: { subdomain: :api }
will not, because request.subdomain
returns 'api'
as a String.
Constraint values should match the corresponding Request object method return type.
There is an exception for the format
constraint, while it's a method on the Request object, it's also an implicit optional parameter on every path. Segment constraints take precedence and the format
constraint is only applied when enforced through a hash. For example, get 'foo', constraints: { format: 'json' }
will match GET /foo
because the format is optional by default.
You can use a lambda like in get 'foo', constraints: lambda { |req| req.format == :json }
to only match the route to explicit JSON requests.
3.10 Advanced Constraints
If you have a more advanced constraint, you can provide an object that responds to matches?
that Rails should use. Let's say you wanted to route all users on a restricted list to the RestrictedListController
. You could do:
class RestrictedListConstraint
def initialize
@ips = RestrictedList.retrieve_ips
end
def matches?(request)
@ips.include?(request.remote_ip)
end
end
Rails.application.routes.draw do
get '*path', to: 'restricted_list#index',
constraints: RestrictedListConstraint.new
end
You can also specify constraints as a lambda:
Rails.application.routes.draw do
get '*path', to: 'restricted_list#index',
constraints: lambda { |request| RestrictedList.retrieve_ips.include?(request.remote_ip) }
end
Both the matches?
method and the lambda gets the request
object as an argument.
3.10.1 Constraints in a Block Form
You can specify constraints in a block form. This is useful for when you need to apply the same rule to several routes. For example:
class RestrictedListConstraint
# ...Same as the example above
end
Rails.application.routes.draw do
constraints(RestrictedListConstraint.new) do
get '*path', to: 'restricted_list#index'
get '*other-path', to: 'other_restricted_list#index'
end
end
You can also use a lambda
:
Rails.application.routes.draw do
constraints(lambda { |request| RestrictedList.retrieve_ips.include?(request.remote_ip) }) do
get '*path', to: 'restricted_list#index'
get '*other-path', to: 'other_restricted_list#index'
end
end
3.11 Wildcard Segments
A route definition can have a wildcard segment, which is a segment prefixed with a star, such as *other
:
get 'photos/*other', to: 'photos#unknown'
Wildcard segments allow for something called "route globbing", which is a way to specify that a particular parameter (*other
above) be matched to the remaining part of a route.
So the above route would match photos/12
or /photos/long/path/to/12
, setting params[:other]
to "12"
or "long/path/to/12"
.
Wildcard segments can occur anywhere in a route. For example:
get 'books/*section/:title', to: 'books#show'
would match books/some/section/last-words-a-memoir
with params[:section]
equals 'some/section'
, and params[:title]
equals 'last-words-a-memoir'
.
Technically, a route can have even more than one wildcard segment. The matcher assigns segments to parameters in the order they occur. For example:
get '*a/foo/*b', to: 'test#index'
would match zoo/woo/foo/bar/baz
with params[:a]
equals 'zoo/woo'
, and params[:b]
equals 'bar/baz'
.
3.12 Format Segments
Given this route definition:
get '*pages', to: 'pages#show'
By requesting '/foo/bar.json'
, your params[:pages]
will be equal to 'foo/bar'
with the request format of JSON in params[:format]
.
The default behavior with format
is that if included Rails automatically captures it from the URL and includes it in params[:format], but format
is not required in a URL.
If you want to match URLs without an explicit format and ignore URLs that include a format extension, you could supply format: false
like this:
get '*pages', to: 'pages#show', format: false
If you want to make the format segment mandatory, so it cannot be omitted, you can supply format: true
like this:
get '*pages', to: 'pages#show', format: true
3.13 Redirection
You can redirect any path to any other path by using the redirect
helper in your router:
get '/stories', to: redirect('/articles')
You can also reuse dynamic segments from the match in the path to redirect to:
get '/stories/:name', to: redirect('/articles/%{name}')
You can also provide a block to redirect
, which receives the symbolized path parameters and the request object:
get '/stories/:name', to: redirect { |path_params, req| "/articles/#{path_params[:name].pluralize}" }
get '/stories', to: redirect { |path_params, req| "/articles/#{req.subdomain}" }
Please note that default redirection is a 301 "Moved Permanently" redirect. Keep in mind that some web browsers or proxy servers will cache this type of redirect, making the old page inaccessible. You can use the :status
option to change the response status:
get '/stories/:name', to: redirect('/articles/%{name}', status: 302)
In all of these cases, if you don't provide the host (http://www.example.com
), Rails will take those details from the current request.
3.14 Routing to Rack Applications
Instead of specifying :to
as a String like 'articles#index'
, which corresponds to the index
method in the ArticlesController
class, you can specify any Rack application as the endpoint for a matcher:
match '/application.js', to: MyRackApp, via: :all
As long as MyRackApp
responds to call
and returns a [status, headers, body]
, the router won't know the difference between the Rack application and a controller action. This is an appropriate use of via: :all
, as you will want to allow your Rack application to handle all verbs.
An interesting tidbit - 'articles#index'
expands out to ArticlesController.action(:index)
, which returns a valid Rack application.
Since procs/lambdas are objects that respond to call
, you can implement very simple routes (e.g. for health checks) inline, something like: get '/health', to: ->(env) { [204, {}, ['']] }
If you specify a Rack application as the endpoint for a matcher, remember that
the route will be unchanged in the receiving application. With the following
route your Rack application should expect the route to be /admin
:
match '/admin', to: AdminApp, via: :all
If you would prefer to have your Rack application receive requests at the root
path instead, use mount
:
mount AdminApp, at: '/admin'
3.15 Using root
You can specify what Rails should route '/'
to with the root
method:
root to: 'pages#main'
root 'pages#main' # shortcut for the above
You typically put the root
route at the top of the file so that it can be matched first.
The root
route primarily handles GET
requests by default. But it is possible to configure it to handle other verbs (e.g. root "posts#index", via: :post
)
You can also use root inside namespaces and scopes as well:
root to: "home#index"
namespace :admin do
root to: "admin#index"
end
The above will match /admin
to the index
action for the AdminController
and match /
to index
action of the HomeController
.
3.16 Unicode Character Routes
You can specify unicode character routes directly. For example:
get 'こんにちは', to: 'welcome#index'
3.17 Direct Routes
You can create custom URL helpers by calling direct
. For example:
direct :homepage do
"https://rubyonrails.org"
end
# >> homepage_url
# => "https://rubyonrails.org"
The return value of the block must be a valid argument for the url_for
method. So, you can pass a valid string URL, Hash, Array, an Active Model instance, or an Active Model class.
direct :commentable do |model|
[ model, anchor: model.dom_id ]
end
direct :main do
{ controller: 'pages', action: 'index', subdomain: 'www' }
end
# >> main_url
# => "http://www.example.com/pages"
3.18 Using resolve
The resolve
method allows customizing polymorphic mapping of models. For example:
resource :basket
resolve("Basket") { [:basket] }
<%= form_with model: @basket do |form| %>
<!-- basket form -->
<% end %>
This will generate the singular URL /basket
instead of the usual /baskets/:id
.
4 Customizing Resourceful Routes
While the default routes and helpers generated by resources
will usually serve you well, you may need to customize them in some way. Rails allows for several different ways to customize the resourceful routes and helpers. This section will detail the available options.
4.1 Specifying a Controller to Use
The :controller
option lets you explicitly specify a controller to use for the resource. For example:
resources :photos, controller: 'images'
will recognize incoming paths beginning with /photos
but route to the Images
controller:
HTTP Verb | Path | Controller#Action | Named Route Helper |
---|---|---|---|
GET | /photos | images#index | photos_path |
GET | /photos/new | images#new | new_photo_path |
POST | /photos | images#create | photos_path |
GET | /photos/:id | images#show | photo_path(:id) |
GET | /photos/:id/edit | images#edit | edit_photo_path(:id) |
PATCH/PUT | /photos/:id | images#update | photo_path(:id) |
DELETE | /photos/:id | images#destroy | photo_path(:id) |
For namespaced controllers you can use the directory notation. For example:
resources :user_permissions, controller: 'admin/user_permissions'
This will route to the Admin::UserPermissionsController
instance.
Only the directory notation is supported. Specifying the controller with
Ruby constant notation (e.g. controller: 'Admin::UserPermissions'
) is not supported.
4.2 Specifying Constraints on id
You can use the :constraints
option to specify a required format on the implicit id
. For example:
resources :photos, constraints: { id: /[A-Z][A-Z][0-9]+/ }
This declaration constrains the :id
parameter to match the given regular expression. The router would no longer match /photos/1
to this route. Instead, /photos/RR27
would match.
You can specify a single constraint to apply to a number of routes by using the block form:
constraints(id: /[A-Z][A-Z][0-9]+/) do
resources :photos
resources :accounts
end
You can use the more advanced constraints available in non-resourceful routes section in this context as well.
By default the :id
parameter doesn't accept dots - this is because the dot is used as a separator for formatted routes. If you need to use a dot within an :id
add a constraint which overrides this - for example id: /[^\/]+/
allows anything except a slash.
4.3 Overriding the Named Route Helpers
The :as
option lets you override the default naming for the route helpers. For example:
resources :photos, as: 'images'
This will match /photos
and route the requests to PhotosController
as usual, but use the value of the :as
option to name the helpers images_path
etc., as shown:
HTTP Verb | Path | Controller#Action | Named Route Helper |
---|---|---|---|
GET | /photos | photos#index | images_path |
GET | /photos/new | photos#new | new_image_path |
POST | /photos | photos#create | images_path |
GET | /photos/:id | photos#show | image_path(:id) |
GET | /photos/:id/edit | photos#edit | edit_image_path(:id) |
PATCH/PUT | /photos/:id | photos#update | image_path(:id) |
DELETE | /photos/:id | photos#destroy | image_path(:id) |
4.4 Renaming the new
and edit
Path Names
The :path_names
option lets you override the default new
and edit
segment in paths. For example:
resources :photos, path_names: { new: 'make', edit: 'change' }
This would allow paths such as /photos/make
and /photos/1/change
instead of /photos/new
and /photos/1/edit
.
The route helpers and controller action names aren't changed by this option. The two paths shown would have new_photo_path
and edit_photo_path
helpers and still route to the new
and edit
actions.
It is also possible to change this option uniformly for all of your routes by using a scope
block:
scope path_names: { new: 'make' } do
# rest of your routes
end
4.5 Prefixing the Named Route Helpers with :as
You can use the :as
option to prefix the named route helpers that Rails generates for a route. Use this option to prevent name collisions between routes using a path scope. For example:
scope 'admin' do
resources :photos, as: 'admin_photos'
end
resources :photos
This changes the route helpers for /admin/photos
from photos_path
,
new_photos_path
, etc. to admin_photos_path
, new_admin_photo_path
, etc.
Without the addition of as: 'admin_photos'
on the scoped resources :photos
,
the non-scoped resources :photos
will not have any route helpers.
To prefix a group of route helpers, use :as
with scope
:
scope 'admin', as: 'admin' do
resources :photos, :accounts
end
resources :photos, :accounts
Just as before, this changes the /admin
scoped resource helpers to
admin_photos_path
and admin_accounts_path
, and allows the non-scoped
resources to use photos_path
and accounts_path
.
The namespace
scope will automatically add :as
as well as :module
and :path
prefixes.
4.6 Using :as
in Nested Resources
The :as
option can override routing helper names for resources in nested routes as well. For example:
resources :magazines do
resources :ads, as: 'periodical_ads'
end
This will create routing helpers such as magazine_periodical_ads_url
and edit_magazine_periodical_ad_path
instead of the default magazine_ads_url
and edit_magazine_ad_path
.
4.7 Parametric Scopes
You can prefix routes with a named parameter:
scope ':account_id', as: 'account', constraints: { account_id: /\d+/ } do
resources :articles
end
This will provide you with paths such as /1/articles/9
and will allow you to reference the account_id
part of the path as params[:account_id]
in controllers, helpers, and views.
It will also generate path and URL helpers prefixed with account_
, into which you can pass your objects as expected:
account_article_path(@account, @article) # => /1/article/9
url_for([@account, @article]) # => /1/article/9
form_with(model: [@account, @article]) # => <form action="/1/article/9" ...>
The :as
option is also not mandatory, but without it, Rails will raise an error when evaluating url_for([@account, @article])
or other helpers that rely on url_for
, such as form_with
.
4.8 Restricting the Routes Created
By default, using resources
creates routes for the seven default actions (index
, show
, new
, create
, edit
, update
, and destroy
). You can use the :only
and :except
options to limit which routes are created.
The :only
option tells Rails to create only the specified routes:
resources :photos, only: [:index, :show]
Now, a GET
request to /photos
or /photos/:id
would succeed, but a POST
request to /photos
will fail to match.
The :except
option specifies a route or list of routes that Rails should not create:
resources :photos, except: :destroy
In this case, Rails will create all of the normal routes except the route for destroy
(a DELETE
request to /photos/:id
).
If your application has many RESTful routes, using :only
and :except
to
generate only the routes that you actually need can cut down on memory use and
speed up the routing process by eliminating unused
routed.
4.9 Translated Paths
Using scope
, we can alter path names generated by resources
:
scope(path_names: { new: 'neu', edit: 'bearbeiten' }) do
resources :categories, path: 'kategorien'
end
Rails now creates routes to the CategoriesController
.
HTTP Verb | Path | Controller#Action | Named Route Helper |
---|---|---|---|
GET | /kategorien | categories#index | categories_path |
GET | /kategorien/neu | categories#new | new_category_path |
POST | /kategorien | categories#create | categories_path |
GET | /kategorien/:id | categories#show | category_path(:id) |
GET | /kategorien/:id/bearbeiten | categories#edit | edit_category_path(:id) |
PATCH/PUT | /kategorien/:id | categories#update | category_path(:id) |
DELETE | /kategorien/:id | categories#destroy | category_path(:id) |
4.10 Specifying the Singular Form of a Resource
If you need to override the singular form of a resource, you can add a rule to Active Support Inflector via inflections
:
ActiveSupport::Inflector.inflections do |inflect|
inflect.irregular 'tooth', 'teeth'
end
4.11 Renaming Default Route Parameter id
It is possible to rename the default parameter name id
with the :param
option. For example:
resources :videos, param: :identifier
Will now use params[:identifier]
instead of params[:id]
.
videos GET /videos(.:format) videos#index
POST /videos(.:format) videos#create
new_video GET /videos/new(.:format) videos#new
edit_video GET /videos/:identifier/edit(.:format) videos#edit
Video.find_by(id: params[:identifier])
# Instead of
Video.find_by(id: params[:id])
You can override ActiveRecord::Base#to_param
of the associated model to construct a URL:
class Video < ApplicationRecord
def to_param
identifier
end
end
irb> video = Video.find_by(identifier: "Roman-Holiday")
irb> edit_video_path(video)
=> "/videos/Roman-Holiday/edit"
5 Inspecting Routes
Rails offers a few different ways of inspecting and testing your routes.
5.1 Listing Existing Routes
To get a complete list of routes available in an application, visit http://localhost:3000/rails/info/routes
in the development environment. You can also execute the bin/rails routes
command in your terminal to get the same output.
Both methods will list all of your routes, in the same order that they appear in config/routes.rb
. For each route, you'll see:
- The route name (if any)
- The HTTP verb used (if the route doesn't respond to all verbs)
- The URL pattern to match
- The routing parameters for the route
For example, here's a small section of the bin/rails routes
output for a RESTful route:
users GET /users(.:format) users#index
POST /users(.:format) users#create
new_user GET /users/new(.:format) users#new
edit_user GET /users/:id/edit(.:format) users#edit
The route name (new_user
above, for example) can be considered the base for deriving route helpers. To get the name of a route helper, add the suffix _path
or _url
to the route name (new_user_path
, for example).
You can also use the --expanded
option to turn on the expanded table formatting mode.
$ bin/rails routes --expanded
--[ Route 1 ]----------------------------------------------------
Prefix | users
Verb | GET
URI | /users(.:format)
Controller#Action | users#index
--[ Route 2 ]----------------------------------------------------
Prefix |
Verb | POST
URI | /users(.:format)
Controller#Action | users#create
--[ Route 3 ]----------------------------------------------------
Prefix | new_user
Verb | GET
URI | /users/new(.:format)
Controller#Action | users#new
--[ Route 4 ]----------------------------------------------------
Prefix | edit_user
Verb | GET
URI | /users/:id/edit(.:format)
Controller#Action | users#edit
5.2 Searching Routes
You can search through your routes with the grep option: -g
. This outputs any routes that partially match the URL helper method name, the HTTP verb, or the URL path.
$ bin/rails routes -g new_comment
$ bin/rails routes -g POST
$ bin/rails routes -g admin
If you only want to see the routes that map to a specific controller, there's the controller option: -c
.
$ bin/rails routes -c users
$ bin/rails routes -c admin/users
$ bin/rails routes -c Comments
$ bin/rails routes -c Articles::CommentsController
The output from bin/rails routes
is easier to read if you widen your terminal window until the output lines don't wrap or use the --expanded
option.
5.3 Listing Unused Routes
You can scan your application for unused routes with the --unused
option. An "unused" route in Rails is a route that is defined in the config/routes.rb file but is not referenced by any controller action or view in your application. For example:
$ bin/rails routes --unused
Found 8 unused routes:
Prefix Verb URI Pattern Controller#Action
people GET /people(.:format) people#index
POST /people(.:format) people#create
new_person GET /people/new(.:format) people#new
edit_person GET /people/:id/edit(.:format) people#edit
person GET /people/:id(.:format) people#show
PATCH /people/:id(.:format) people#update
PUT /people/:id(.:format) people#update
DELETE /people/:id(.:format) people#destroy
5.4 Routes in Rails Console
You can access route helpers using Rails.application.routes.url_helpers
within the Rails Console. They are also available via the app object. For example:
irb> Rails.application.routes.url_helpers.users_path
=> "/users"
irb> user = User.first
=> #<User:0x00007fc1eab81628
irb> app.edit_user_path(user)
=> "/users/1/edit"
6 Testing Routes
Rails offers three built-in assertions designed to make testing routes simpler:
6.1 The assert_generates
Assertion
assert_generates
asserts that a particular set of options generate a particular path and can be used with default routes or custom routes. For example:
assert_generates '/photos/1', { controller: 'photos', action: 'show', id: '1' }
assert_generates '/about', controller: 'pages', action: 'about'
6.2 The assert_recognizes
Assertion
assert_recognizes
is the inverse of assert_generates
. It asserts that a given path is recognized and routes it to a particular spot in your application. For example:
assert_recognizes({ controller: 'photos', action: 'show', id: '1' }, '/photos/1')
You can supply a :method
argument to specify the HTTP verb:
assert_recognizes({ controller: 'photos', action: 'create' }, { path: 'photos', method: :post })
6.3 The assert_routing
Assertion
The assert_routing
assertion checks the route both ways. It combines the functionality of both assert_generates
and assert_recognizes
. It tests that the path generates the options, and that the options generate the path:
assert_routing({ path: 'photos', method: :post }, { controller: 'photos', action: 'create' })
7 Breaking Up a Large Route File With draw
In a large application with thousands of routes, a single config/routes.rb
file can become cumbersome and hard to read. Rails offers a way to break up a single routes.rb
file into multiple small ones using the draw
macro.
For example, you could add an admin.rb
file that contains all the routes related to the admin area, another api.rb
file for API related resources, etc.
# config/routes.rb
Rails.application.routes.draw do
get 'foo', to: 'foo#bar'
draw(:admin) # Will load another route file located in `config/routes/admin.rb`
end
# config/routes/admin.rb
namespace :admin do
resources :comments
end
Calling draw(:admin)
inside the Rails.application.routes.draw
block itself
will try to load a route file that has the same name as the argument given
(admin.rb
in this example). The file needs to be located inside the
config/routes
directory or any sub-directory (i.e. config/routes/admin.rb
or
config/routes/external/admin.rb
).
You can use the normal routing DSL inside a secondary routing file such as admin.rb
, but do not surround it with the Rails.application.routes.draw
block. That should be used in the main config/routes.rb
file only.
Don't use this feature unless you really need it. Having multiple routing files make it harder to discover routes in one place. For most applications - even those with a few hundred routes - it's easier for developers to have a single routing file. The Rails routing DSL already offers a way to break routes in an organized manner with namespace
and scope
.
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